The present invention generally relates to a medical device for stimulating tissue in a living body, and more particularly relates to a multi-contact connector for use with such medical devices.
A variety of neurostimulation systems include an array of electrodes, formed on a lead, that are electrically connected to an implanted electronic package. Often, the electrical connection is achieved in part via one or more lead extensions that connect to the electronic package at a proximal end and connect to the lead carrying the electrode array at a distal end (and together with the lead carrying the electrode array, may be called a lead system). For instance, for a typical neurostimulation system, the proximal end of one or more lead extensions is connected to an implanted pulse generator, while the distal end of the lead extension(s) connects to one or more leads bearing electrode arrays, which electrodes are positioned in the spinal column.
For many neurostimulation systems, it is common to perform a xe2x80x9ctrial stimulationxe2x80x9d wherein the electrodes are positioned at the target location, while a pulse generator remains external to the patient during the trial period. For a number of days, the patient""s response to a variety of stimulation parameters is gauged, prior to performing the surgical procedure of implanting the pulse generator in the patient""s body. If the patient""s response to the trial stimulation is not acceptable, the pulse generator is simply not implanted, and only the electrode array/lead system needs to be removed.
For the trial stimulation period, a lead extension commonly called a percutaneous lead extension connects, at its distal end, to the proximal end of the electrode array lead. The percutaneous lead extension lies in a tunnel through body tissues and extends outside the body, where its proximal end is connected (possibly via an additional external cable) to an external xe2x80x9ctrial stimulator.xe2x80x9d
A typical surgical process for implanting a trial stimulation system includes first using an electrode insertion needle to implant the electrode array so that the electrodes are positioned at the target stimulation site. The electrode insertion needle is a hollow needle preferably carrying a removable solid-core stylet. After the needle is situated, the stylet is removed, leaving a hollow opening. To ensure the needle tip has entered the epidural space, a loss of resistance procedure is typically employed.
To prevent damage to the electrode array, a lead blank that approximates the diameter of the electrode array lead may be inserted into the needle to clear away any tissue obstructing the path through the needle and into the epidural space. The lead blank is then removed and the electrode array is passed through the needle and cleared path into the epidural space.
When the series of electrodes are in the general vicinity of the target, the physician fine-tunes placement by connecting the electrode array to an external trial stimulator and soliciting patient feedback of paresthesia for each electrode. After the electrode array is properly positioned, the needle must be removed, either by pulling it out over the end of the electrode array""s lead, or by disassembly if the connector at the proximal end of the electrode array is larger than the needle. With the array positioned at the target site, the surgeon secures the lead by making an incision near the point where the lead enters the spine. The lead is secured at that point via a lead anchor.
The physician then creates a tunnel between the anchored, proximal end of the electrode array and the percutaneous exit site (i.e., the location where the percutaneous lead extension exits the body through the skin). At the incision where the lead is anchored, the distal end of the percutaneous lead extension is connected to the proximal end of the electrode array. A tunneling tool is used to create the tunnel from the percutaneous exit site to this same incision. The proximal end of the percutaneous lead extension is attached to the tunneling tool, which pulls the proximal end of the extension back through the tunnel as the tool is removed, and out through the percutaneous exit site. The proximal end of the percutaneous extension, now protruding through the skin, is connected to the trial stimulator cable (possibly via an additional external cable).
The percutaneous extension preferably has a small connector at its proximal end to minimize the diameter of the tunnel through which the extension is pulled. The larger the tunnel, the more tissue trauma, post surgical pain, recovery time, and possibility of infection.
In addition, for some patients, two electrode arrays are used. With current designs, the surgeon typically creates a separate subcutaneous tunnel for each percutaneous extension. It would be a great advantage to need only one extension and one subcutaneous tunnel.
Additionally, current connector designs typically have four or eight contacts per connector pin. To increase the number of contacts per connector, a connector with two (or more) pins is typically used. This is often referred to as a dual connector.
A need exists for more compact electrical connections, both inside and outside the body. In addition, a need exists for a greater number of contacts per connector, without increasing the size of the connector or space required for the connector receptacle within an electronic package.
In view of the above, it would be preferable to have a single percutaneous extension with a proximal connector having, for example, 16 contacts on one small-diameter pin. The number of subcutaneous tunnels would preferably be reduced to one, and the size of the tunnel required to draw the connector through the tunnel would also preferably be minimized.
The receptacle portion of the connection currently faces the same limitation regarding number of contacts versus connector size. For instance, available 16-contact connectors result in a receptacle size that greatly impacts the overall size of an electronic package. By creating a receptacle that accepts a connector with a single small-diameter 16-contact pin, the electronic device size is significantly reduced.
Other connection points within a trial stimulation setting and within a xe2x80x9cpermanentxe2x80x9d stimulation setting can benefit from a design with the improvements described herein. For instance, connections within the body, such as between the electrode array lead or internal extension and the implanted pulse generator, are generally quite bulky, especially for 16-contact (16-electrode) configurations.
As such, the invention disclosed and claimed herein provides a tool-less connector with multiple contacts and a compact design. As a result, using this connector, e.g., within a trial stimulator setting, a minimally invasive subcutaneous tunnel can be created which should reduce tissue healing time, patient discomfort, and infection risk. Advantageously, providing additional contacts allows enhanced stimulation protocols and/or additional channels for other purposes, such as for feedback. In some embodiments of the invention, the mating receptacle of the connector allows for multiple contacts while minimizing the space required for the increased number of contacts.
One embodiment of the present invention provides a connector pin containing multiple in-line contacts. Each xe2x80x9clinexe2x80x9d consists of a row of independent contacts arranged in a linear array spaced along the long axis of the pin. Each contact is connected to a conductor that lies within the pin. Each conductor extends out through the end of the pin and into a cable. This cable may be the body of a percutaneous lead extension, an internal lead extension, or any of a number of other components within a trial or xe2x80x9cpermanentxe2x80x9d stimulation setting.
In other embodiments of the present invention, a receptacle is provided that has contacts arranged to align with the matching contacts on the connector pin.
Additional embodiments of the invention provide contacts that may be in the form of spring loaded pins or leaf-style springs.
Yet other embodiments of the invention provide features that prevent the contacts on the connector pin from touching the contacts on the receptacle until all contacts are appropriately aligned.
Thus, the present invention provides connector pins that allow, inter alia, the diameter of a tunnel created for a percutaneous lead extension to be minimized. By reducing the tunnel diameter, recovery time, patient discomfort, and possibility of infection are reduced. Using subject connectors/receptacles in other system locations offers similar advantages due to the decreased area affected by the surgery and the implanted components.
Other advantages of the present invention include (but are not limited to) decreased size of any electrical device that houses a receptacle for a subject connector, access to a greater number of simulation alternatives or other use of additional channels, enhanced pin-to-receptacle contact schemes, and tool-less operation of the connection. The connector pins of the present invention may be used advantageously wherever an electrical connection is required, such as between the percutaneous extension and any external cable, between the percutaneous extension and the trial stimulator, and/or between the fully implanted extension and the implanted pulse generator.